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Group website

Sometime during the first year of our group I asked one of my graduate students to put together a group website. “Let’s first finish our first paper” he replied. This attitude shows how seriously we take websites. Not just anything deserves to have a website. Only things of staggering beautymind-blowing webdesign or the friendliest user interface can be websites. Still,

https://frolovlab.org/

Now that our group has fired out the first series of papers, and even though the papers are still painfully making their way through the antiquated journal system, it is time to unveil a modest yet informative little website.

As a side effect, since this blog no longer represents our whole group my hands are now officially untied, and I can proclaim the most ridiculous thoughts here.

First paper finished

High critical magnetic field superconducting contacts to Ge/Si core/shell nanowires

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My group has crossed an important milestone today – we have finalized and uploaded to arxiv our first publication. We are working on several of them simultaneously, and by the luck of the draw the first one out is a paper in which we share our experience making a particular type of nanowire superconducting.

The one and only good thing about writing papers is that it stimulates the authors to think about the experiment they have done in a special way: to find explanations for strange values and effects that only come forward when you give it that extra careful look. That tenth reading that you do under duress of scientific correctness. When we transition into the era of open science, we will share all our results on the fly, and look like fools for all our misconceptions and mistakes, but we will correct each other and move forward much faster. We will parallelize our intellects to think about each other’s work and won’t need to read the same text over and over again not to miss an embarassing mistake.

For now we just keep writing papers.

Excellent tutorial on one-dimensional systems

Should arxiv have ranking and annotation features?

Arxiv.org is a great resource where many, if not the majority, of results in my field appear long before formal publication in journals. In fact, I don’t have a habit of reading physics journals anymore, but I daily look through new postings on arxiv.I also have two papers submitted only to arxiv, and not to any old-fashioned journal.

That said, arxiv is stuck in the 1990’ies with its focus on lists, TeX, its awkward search and lack of any social network functions. Since it is such a convergence point for the physics community, its backwardness has grown into a serious limiting factor for the free and open scientific process. In other words, what it offers – namely instant publication – is better than what journals offer, but this has in the meantime become the new normal. While what it does not offer is holding us back.

This can be seen in the new massive survey that arxiv has conducted of its own users. In a long list of boring questions about tiny incremental improvements to the website, there is a very important category they called ‘New Services’. You will see that over 55% of survey respondents say that ranking and comment functions, familiar from social networks, reddits, and just, ahem, the entire internet, are either ‘Very Important’ or ‘Somewhat Important’. A smaller majority has just taken the UK out of the EU!

Yet the arxiv program director at Cornell Oya Rieger writes about it as an even split between those who are strongly for these features (~35%) and those strongly against (~35%). She goes on an on about caution and caveats, which basically means that her and the arxiv team are not going to do this on their own. She does mention that the support for these features is stronger among younger users, so there may be a generational divide at play here, and the arxiv team is on the wrong side of this divide from the historical point of view.

Think about it: all of arxiv content is open to the entire internet. If somebody makes a different website which implements these annotation, ranking, search, communication features nicely, and if the community starts using that service, then not having these features as part of arxiv.org itself will be akin to hiding one’s head in the sand – ignoring the new norm that just grew around you. Now, this has not happened yet, but the demand for it is clearly present, as the survey results demonstrate. When this finally happens, it will be the beginning of the end of arxiv, as at that point it will be easier to submit your work to the new website where it can be instantly evaluated, discussed, ranked, categorized and improved through community interactions.

Nanolithography Expert Position

University of Pittsburgh Peteresen Institute of Nanoscience and Engineering is hiring a PhD-level expert in electron beam and optical lithography. This job is for someone to develop lithography processes in close cooperation with research groups at Pitt, and to take full advantage of the Raith e-Line system, as well as of the  brand new Elionix 100kV machine that is shortly arriving to the Carnegie Mellon cleanroom next doors. Our nano team, once complete, will have four PhD-level experts in different areas of nanofabrication and nanocharacterization.

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Full job announcement can be found here

Commercializing your Research

Sometimes I stay awake in the night thinking – how soon will the results of my work become useful for humanity? Well, better get up and do something about it! And so a few months ago we have started a new scientific equipment company, based on research breakthroughs in the field of topological quantum matter.

The new company is called ‘Pittsburgh Instruments’ to honor the long-standing tradition of naming something after a city. We currently have three employees, and a distinguished board of advisers though some of the founders of our technology are sadly, no longer with us. The website for the company, along with the Kickstarter page are going online as I write this.

We actually already have a prototype of our first instrument. Please welcome:

Chernnumberometer 1.0 from Pittsburgh Instruments, going on sale December 31 2016

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It is a sleekly designed high tech gadget which can measure a Chern number of anything that fits inside! Just open the door, put your item of choice in.Select Integration Time. Press start. The machine will rotate the object to examine it. Then the digital display will show you the answer. For example, if you put a doughnut inside it will read 0, if you put an orange it will read 1. You can read pretty high numbers if you put in something like this. Give it a try! You can also easily switch a topological invariant that you want to measure from Chern number to a Z2 or a determinant of a scattering matrix for 1D systems. Nevermind that labels say ‘Chicken’ or ‘Popcorn’ – this is an inside joke from the company, we like to be cool like Android developers. For example ‘Defrost’ refers to a very advanced renormalization group-based algorithm.

Our target population are theoretical physicists who have an incessant desire to know things about physical systems that cannot be measured. This compact and elegant Chernnumberometer fits on an office desk, in the coffee area or even at your house! Priced at just $3,999 it also fits on almost any grant. Make sure to mention it in your next proposal!

(Some of the issues we are still working out are dynamic cooling, as certain samples we reported to get very hot. The final release might actually feature a helium compressor bumping the price to $53,999. Also, don’t try to measure Chern numbers of your pets or eggs)

Spin Transistor Explanation

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This gif filmed in Tofino is from 2008 and it explains the ‘injector-detector’ device used to generate and measure spin currents. Charge currents flow to the left, while spin currents flow both ways.

It pertains, for example, to this paper we wrote: http://arxiv.org/abs/1208.3106 (this is an arxiv-only publication!)

 

Introduction to Solid State Physics

Last semester I recorded 23 lectures on Solid State Physics for Undergraduate students. The first 15 lectures are following the wonderful texbook by Steven Simon “Oxford Solid State Basics”, and the last lectures cover superconductivity and advanced topics from Quantum Transport. This class can be a prequel to my Quantum Transport course and I hope it will be useful for students thinking of going into condensed matter research.

Because this is so great for binge watching, I am releasing the whole season at once.

Back to the Future

So there is this great movie that you should totally go see, it is about an eccentric scientist who befriends a simple-minded neighborhood teenager and sends him backwards in time in a car converted into a time machine…

Something like this just happened in our lab. We started out a couple of years ago as a cryogen-free operation. Instead of relying of liquid helium, we used closed-cycle cryostats where helium circulates between a compressor and a cryostat and extracts heat from a vacuum-shielded volume. There are two reasons why cryogen-free systems are great – they save money on (pricey) liquid helium and they are easy to operate at a push of a button.

But in the meantime our generous university set up a helium liquefier, which supplies nearly-free liquid helium to us. And so now we built our first liquid helium setup – a dunker stick! It derives its name from a concept of dunking your specimen into liquid helium in order to reach a low temperature of 4.2 Kelvin, at which helium is stored in liquid form.

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From the technological point of view, it is a step back compared to our cryofree setups. But we can use it for many quick measurements and tests, which is great.

Miro at the Nanoscale

Optical microscopy images of a silicon wafer covered with PMMA and silicon nitride. The structures appeared when silicon nitride was sputtered onto the wafer.

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Rashba Effect at 35

Last year was the 35th anniversary of the seminal paper by Bychkov and Rashba which introduced a spin-orbit coupling which is now known as “the Rashba effect“. It is a beautiful piece of physics that brings a bit of relativity into condensed matter world. Turns out, in an electric field (or under a broken symmetry) electron spins in a solid can behave as if they are in a magnetic field.

Anyhow, 35 years later the Rashba effect lives on and find itself at the frontiers of some of the hottest research of the 21-st century, as you can convince yourself by arxiving it (it is like googling but with arxiv.org).

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So a few months ago Aurelien Manchon approached me and several other folks to be part of a review of what is the face of Rashba effect 35 years later. As with all manuscripts, preparation took forever, so we are celebrating the 35th birthday of Rashba effect one year later. But finally the paper it out there and we are hoping it can serve those who want to know how Rashba spin-orbit physics beats along with spintronics, quantum computing, topological physics and cold atomic research.

I learned a lot about spin-orbit interaction myself from working on this review, I also learned the difference between stirring and steering, as in ‘steering wheel’ not ‘stirring wheel’ (thank you, anonymous referee!).

Helium Liquefier

Our University has sacrificed a parking lot to realize this project:

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It is an expansion to the machine shop which among other things now hosts this helium liquefier:

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Our lab is now connected to the helium recovery system, and we are building our first “wet” cryostat in which liquefied helium is used to cool a sample to 4.2 degrees Kelvin (-269 degrees centigrade). We are also now officially shopping for a used wet dilution refrigerator.

Quantum Triangles

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A friend once told me that all that physicists ever measure is either a sine wave or a straight line. Nothing proves him wrong better than this piece of data we obtained by measuring on a semiconductor nanowire device (Ge/Si nanowires). These double-triangles represent a charge stability diagram of a double quantum dot. Charge stability actually happens in between the triangles, where current is zero (blue), and the number of charges on each of the two quantum dots is fixed. We don’t know how many charges are there on each dot but it is few tens. In the triangular regions, charges move because they have enough energy to jump from one quantum dot into the other and out into the lead that takes them to our ammeter. Inside the triangles, we get a glimpse of quantum energy levels, orbital and spin, of the particles trapped in quantum dots – those energy levels are the stripes of the triangles. The axes of the graphs are voltages on remote electrodes located 10 nanometers away from the nanowire, voltages on these electrodes (gates) are used to change the capacitive energy of the quantum dots.

Pittsburgh Nano Jobs

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Our university’s Nanoscience Institute (PINSE) is looking for a Technical Director to run the nanofabrication and characterization facility. The job is part of a major reinvestment effort, and the new Director will play a central role in how the facility will look and operate going forward. We want to attract a truly outstanding candidate, so we are trying to spread the word as far and wide as we can.

The job ad is here: PINSE Technical Director

http://nano.pitt.edu/

Happy 2015!

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Wish you all great discoveries and a lot of fun with science.

Learn about Topological Effects Online

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Several young theorists from Delft and Maryland have put together an online course on ‘Topology in Condensed Matter’.

https://www.edx.org/course/delftx/delftx-topocmx-topology-condensed-matter-6331#.VIhbGzHF-So

The course starts February 9, reserve your spot now! There is no room for everyone on the internet.

Universal glory here we come

Finally the ultimate geeks of the internet caught up with topological quantum computing. (You would think they would be the first to figure it out)

PhD Comics interviews Caltech theorists Gil Refael and Jason Alicea on the subject of anyons. Our Delft device makes a cameo.

And here is a recent article from MIT Technology Review talking about the hardware aspects of this:

http://www.technologyreview.com/featuredstory/531606/microsofts-quantum-mechanics/

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Hmm….

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Graduate prayer

Long-long time ago when I was a graduate student chasing, as most of us, a wild vision of my great advisor, I found myself trying again and again to fabricate devices in the cleanroom, cool them down, measure them – with no luck! My aspiration was to observe amazing never before seen physics, yet I could not even see the things from many decades ago like the supercurrent. At that point, as an act of Universal discourse, I printed a small request on a sheet of paper and posted it on the wall in front of my measurement computer. It said ‘DEAR SOMETHING, PLEASE WORK!’. Time passed, and through sweat and pain the god of Something bestowed her benevolence on me. I saw the supercurrent – I was so happy I called my advisor late in the evening. (I haven’t been so excited since I have spotted a guy named ‘Larry Cooper’ at my first March Meeting and took him for Leon Cooper, the discoverer of Cooper pairs and of mini-Cooper cars).

Anyhow, when I visited my old lab in Urbana last year my prayer was still attached to the wall. Only it was the second one. To the God of Everything.

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For an experiment to be successful, EVERYTHING has to work. And for me supercurrent was only the beginning. Once you got something working, your appetite and your paranoia grow exponentially. We are at this point right now at Pitt. As soon as everything works, something will come out.

Helium Liquefier

The construction of a facility to liquefy helium has started in the back of the Physics building at Pitt. Liquid helium is the blood of most cryogenic experiments, it becomes liquid at 4.2 degrees Kelvin (which is cold) and simply immersing your experiment into this liquid gives you this low temperature.

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So far the project literally only scratched the surface, in a short while a new space will be added to host this helium equipment. Pitt is very much forward-looking with this new construction. The prices of helium gas have been going up, and combined with liquefaction costs they more and more often make low temperature experiments simply unaffordable. What makes our liquefier cost-effective is that it comes with a recovery system: helium that boils off in the labs around campus will be pumped back to the liquefier rather than lost into atmosphere. Our lab was already constructed with recovery plumbing, so we will be able to use local organic liquid helium from a friendly liquefactor down the street.